Continuous digester

Abstract

An apparatus for use in the continuous treatment of cellulosic matter to improve the digestibility thereof, comprising means for receiving finely divided cellulosic matter, acidic process chemicals, and steam; a first attrition mill wherein the steam, cellulosic matter, and process chemicals are intimately mixed and initially reacted; a reactor with rotatable sweeps therein to complete the reaction; and a second attrition mill wherein the reacted material is neutralized to the desired level.

What is claimed is: 
     
       1. Apparatus for the continuous chemical conversion of cellulosic material to a digestible ruminant feed which comprises: means for rapidly and intimately mixing cellulosic material at atmospheric pressure with steam and acidic process chemicals at an elevated pressure;   a reactor housing providing a vertical reaction chamber, an inlet port in open communication with the upper portion of said vertical reaction chamber, and an outlet port in open communication with the bottom portion of said reaction chamber, said reactor housing being capable of withstanding operating pressures of 3 to 10 atmospheres;   means for directing the mixed cellulosic material, steam and acidic process chemicals at the elevated pressure to the reaction chamber through the reactor housing inlet port;   means for removing the acidic reaction products from the outlet port of the reactor housing;   means for mixing the removed acidic reaction products with neutralizing process chemicals to produce a neutralized feed; and   means for discharging the neutralized feed from the apparatus while maintaining back pressure on the reaction chamber.   
     
     
       2. Apparatus, as recited in claim 1, further comprising: means disposed within the reaction chamber for preventing bridging of the reactor contents.   
     
     
       3. Apparatus, as recited in claim 2, wherein the means for mixing the removed acidic reaction products with neutralizing process chemicals to produce a neutralized feed comprises: a neutralizing attrition mill having an inlet eye for receiving the removed acidic reaction products and a discharge outlet for the neutralized feed, which mill is capable of operating under a pressure of 3 to 10 atmospheres; and   means in communication with the neutralizing attrition mill for introducing neutralizing process chemicals to the eye of said mill.   
     
     
       4. Apparatus, as recited in claim 3, wherein the means for removing the acidic reaction products from the outlet port of the reaction housing comprises: screw feeder means, connected between the reactor housing and the neutralizing attrition mill and in open communication with the reaction chamber through the outlet port and in open communication with the eye of the neutralizing attrition mill, for conveying the acidic reaction products to the eye of the neutralizing attrition mill, said screw feeder means being capable of operating under a pressure of 3 to 10 atmospheres.   
     
     
       5. Apparatus, as recited in claim 4, wherein the means for discharging the neutralized feed while maintaining back pressure on the reaction chamber, comprises: a valve means, operably connected to the discharge outlet of the neutralizing attrition mill and having shear capability, for discharging the neutralized feed.   
     
     
       6. Apparatus, as recited in claim 5, wherein the means for mixing cellulosic material at atmospheric pressure with steam and acidic process chemicals at an elevated pressure, comprises: a receiver housing providing a receiver chamber and having an opening in open communication with the chamber for receiving cellulosic material, inlet means in open communication with the chamber for receiving steam, and a bottom discharge outlet in open communication with the chamber for discharging the steam and cellulosic material, which housing is capable of withstanding pressures in the range of 3 to 10 atmospheres;   means connected to the receiver housing for transferring cellulosic material at atmospheric pressure to the receiver chamber when said chamber is operated at an elevated pressure without incurring significant pressure loss from said chamber;   an acidic attrition mill, having an inlet eye for receiving the cellulosic material and steam and a discharge outlet for the pulverized cellulosic material which is capable of operating under a pressure of 3 to 10 atmospheres;   second screw feeder means connected between the receiver housing and the acidic attrition mill in open communication with the receiver chamber through the bottom discharge outlet of the receiver housing and in open communication with the eye of the acidic attrition mill for conveying cellulosic material from the bottom of the receiver housing to the eye of the acidic attrition mill, said feeder means being capable of operating under a pressure of 3 to 10 atmospheres; and   means in open communication with the eye of the acidic attrition mill for introducing acidic digestion chemicals to the interior thereof.   
     
     
       7. Apparatus, as recited in claim 6, wherein the means connected to the receiver housing for transferring cellulosic material at atmospheric pressure to the receiver chamber comprises: a hopper, providing a hopper chamber and having an opening at the top thereof in open communication with the atmosphere for receiving cellulosic material, and an opening in the bottom thereof for the discharge of said cellulosic material; and   plug plunger screw feeder means connected between the hopper and the receiver housing in open communication with the hopper chamber to the bottom discharge opening and in open communication with the receiver chamber through the receiver housing opening for receiving the cellulosic material, for conveying the cellulosic material from the bottom of the hopper to the receiver chamber, while maintaining the pressure in said receiver chamber.   
     
     
       8. Apparatus, as recited in claim 6, wherein the means connected to the receiver housing for transferring cellulosic material at atmospheric pressure to the receiver chamber, comprises: a hopper, disposed above the receiver housing, providing a hopper chamber having an opening in the top thereof in open communication with the atmosphere for receiving cellulosic material, and an opening in the bottom thereof for the discharge of said cellulosic material; and   star valve means connected between the hopper and the receiver housing in open communication with the hopper chamber through the bottom discharge opening and in open communication with the receiver chamber through the receiver housing opening for conveying the cellulosic material from the bottom of the hopper to the receiver chamber, while maintaining pressure in said receiver chamber.